Each importer can now provide an invalidate_mappings callback.

This allows the exporter to provide the mappings without the need to pin
the backing store.

v2: don't try to invalidate mappings when the callback is NULL,
    lock the reservation obj while using the attachments,
    add helper to set the callback
v3: move flag for invalidation support into the DMA-buf,
    use new attach_info structure to set the callback
v4: use importer_priv field instead of mangling exporter priv.

Signed-off-by: Christian König <christian.koe...@amd.com>
---
 drivers/dma-buf/dma-buf.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 include/linux/dma-buf.h   | 36 ++++++++++++++++++++++++++++++++++--
 2 files changed, 78 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 4b46982c6d9c..ffdaab10e2f2 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -565,6 +565,8 @@ struct dma_buf_attachment *dma_buf_attach(const struct 
dma_buf_attach_info *info
 
        attach->dev = info->dev;
        attach->dmabuf = dmabuf;
+       attach->importer_priv = info->importer_priv;
+       attach->invalidate = info->invalidate;
 
        mutex_lock(&dmabuf->lock);
 
@@ -573,7 +575,9 @@ struct dma_buf_attachment *dma_buf_attach(const struct 
dma_buf_attach_info *info
                if (ret)
                        goto err_attach;
        }
+       reservation_object_lock(dmabuf->resv, NULL);
        list_add(&attach->node, &dmabuf->attachments);
+       reservation_object_unlock(dmabuf->resv);
 
        mutex_unlock(&dmabuf->lock);
        return attach;
@@ -599,7 +603,9 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct 
dma_buf_attachment *attach)
                return;
 
        mutex_lock(&dmabuf->lock);
+       reservation_object_lock(dmabuf->resv, NULL);
        list_del(&attach->node);
+       reservation_object_unlock(dmabuf->resv);
        if (dmabuf->ops->detach)
                dmabuf->ops->detach(dmabuf, attach);
 
@@ -633,10 +639,23 @@ struct sg_table *dma_buf_map_attachment(struct 
dma_buf_attachment *attach,
        if (WARN_ON(!attach || !attach->dmabuf))
                return ERR_PTR(-EINVAL);
 
+       /*
+        * Mapping a DMA-buf can trigger its invalidation, prevent sending this
+        * event to the caller by temporary removing this attachment from the
+        * list.
+        */
+       if (attach->invalidate) {
+               reservation_object_assert_held(attach->dmabuf->resv);
+               list_del(&attach->node);
+       }
+
        sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
        if (!sg_table)
                sg_table = ERR_PTR(-ENOMEM);
 
+       if (attach->invalidate)
+               list_add(&attach->node, &attach->dmabuf->attachments);
+
        return sg_table;
 }
 EXPORT_SYMBOL_GPL(dma_buf_map_attachment);
@@ -657,6 +676,9 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment 
*attach,
 {
        might_sleep();
 
+       if (attach->invalidate)
+               reservation_object_assert_held(attach->dmabuf->resv);
+
        if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
                return;
 
@@ -665,6 +687,26 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment 
*attach,
 }
 EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
 
+/**
+ * dma_buf_invalidate_mappings - invalidate all mappings of this dma_buf
+ *
+ * @dmabuf:    [in]    buffer which mappings should be invalidated
+ *
+ * Informs all attachmenst that they need to destroy and recreated all their
+ * mappings.
+ */
+void dma_buf_invalidate_mappings(struct dma_buf *dmabuf)
+{
+       struct dma_buf_attachment *attach;
+
+       reservation_object_assert_held(dmabuf->resv);
+
+       list_for_each_entry(attach, &dmabuf->attachments, node)
+               if (attach->invalidate)
+                       attach->invalidate(attach);
+}
+EXPORT_SYMBOL_GPL(dma_buf_invalidate_mappings);
+
 /**
  * DOC: cpu access
  *
@@ -1122,10 +1164,12 @@ static int dma_buf_debug_show(struct seq_file *s, void 
*unused)
                seq_puts(s, "\tAttached Devices:\n");
                attach_count = 0;
 
+               reservation_object_lock(buf_obj->resv, NULL);
                list_for_each_entry(attach_obj, &buf_obj->attachments, node) {
                        seq_printf(s, "\t%s\n", dev_name(attach_obj->dev));
                        attach_count++;
                }
+               reservation_object_unlock(buf_obj->resv);
 
                seq_printf(s, "Total %d devices attached\n\n",
                                attach_count);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 414b4dde5eb7..566503dd2b4f 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -270,6 +270,8 @@ struct dma_buf_ops {
  * @poll: for userspace poll support
  * @cb_excl: for userspace poll support
  * @cb_shared: for userspace poll support
+ * @invalidation_supported: True when the exporter supports unpinned operation
+ *                          using the reservation lock.
  *
  * This represents a shared buffer, created by calling dma_buf_export(). The
  * userspace representation is a normal file descriptor, which can be created 
by
@@ -293,6 +295,7 @@ struct dma_buf {
        struct list_head list_node;
        void *priv;
        struct reservation_object *resv;
+       bool invalidation_supported;
 
        /* poll support */
        wait_queue_head_t poll;
@@ -311,6 +314,7 @@ struct dma_buf {
  * @dev: device attached to the buffer.
  * @node: list of dma_buf_attachment.
  * @priv: exporter specific attachment data.
+ * @importer_priv: importer specific attachment data.
  *
  * This structure holds the attachment information between the dma_buf buffer
  * and its user device(s). The list contains one attachment struct per device
@@ -326,6 +330,29 @@ struct dma_buf_attachment {
        struct device *dev;
        struct list_head node;
        void *priv;
+       void *importer_priv;
+
+       /**
+        * @invalidate:
+        *
+        * Optional callback provided by the importer of the dma-buf.
+        *
+        * If provided the exporter can avoid pinning the backing store while
+        * mappings exists.
+        *
+        * The function is called with the lock of the reservation object
+        * associated with the dma_buf held and the mapping function must be
+        * called with this lock held as well. This makes sure that no mapping
+        * is created concurrently with an ongoing invalidation.
+        *
+        * After the callback all existing mappings are still valid until all
+        * fences in the dma_bufs reservation object are signaled, but should be
+        * destroyed by the importer as soon as possible.
+        *
+        * New mappings can be created immediately, but can't be used before the
+        * exclusive fence in the dma_bufs reservation object is signaled.
+        */
+       void (*invalidate)(struct dma_buf_attachment *attach);
 };
 
 /**
@@ -364,8 +391,10 @@ struct dma_buf_export_info {
 
 /**
  * struct dma_buf_attach_info - holds information needed to attach to a dma_buf
- * @dmabuf:    the exported dma_buf
- * @dev:       the device which wants to import the attachment
+ * @dmabuf:            the exported dma_buf
+ * @dev:               the device which wants to import the attachment
+ * @importer_priv:     private data of importer to this attachment
+ * @invalidate:                callback to use for invalidating mappings
  *
  * This structure holds the information required to attach to a buffer. Used
  * with dma_buf_attach() only.
@@ -373,6 +402,8 @@ struct dma_buf_export_info {
 struct dma_buf_attach_info {
        struct dma_buf *dmabuf;
        struct device *dev;
+       void *importer_priv;
+       void (*invalidate)(struct dma_buf_attachment *attach);
 };
 
 /**
@@ -404,6 +435,7 @@ struct sg_table *dma_buf_map_attachment(struct 
dma_buf_attachment *,
                                        enum dma_data_direction);
 void dma_buf_unmap_attachment(struct dma_buf_attachment *, struct sg_table *,
                                enum dma_data_direction);
+void dma_buf_invalidate_mappings(struct dma_buf *dma_buf);
 int dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
                             enum dma_data_direction dir);
 int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
-- 
2.14.1

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